America's National Security Agency (NSA) is a cryptologic intelligence agency of the United States Department of Defence responsible for the collection and analysis of foreign communications and foreign signals intelligence. The NSA is a key component of the US Intelligence community, which is headed by the Director of National Intelligence. By law, the NSA's intelligence gathering is limited to foreign communications although there have been some incidents involving domestic collection, including the NSA warrantless surveillance controversy.

A US official has acknowledged that the NSA likely scoops up data on congressional telephone communications but stopped short of saying whether such action extended to calls made by President Barack Obama.

The tense exchange occurred on Tuesday during a hearing on the status of the administration's reforms of the bulk data collection programme exposed last year by former National Security Agency contractor Edward Snowden.

Deputy Attorney General James Cole, testifying before the House Judiciary Committee, hesitated when asked whether the controversial NSA programme that gathers the numbers, call times and lengths of virtually every US phone call extended to communications by members of Congress and executive branch officials.

Congressman Darrell Issa, a House Republican known for his criticism of the Obama White House, asked specifically whether the programme was scooping up information from "202-225-and four digits", the phone exchange for House of Representatives offices.

"Without going specifically, probably we do, congressman," Cole said.

Issa then asked whether the president's phone calls were targeted by the programme.

"I believe every phone number that is with the providers that get those orders comes in under the scope of that order," Cole said, without clarifying whether the president's phones fell within such an order.

Cole agreed to get back to Issa with clarification, to which Issa responded: "Especially if he [Obama] calls Chancellor Merkel."

The remark was an apparent swipe at charges that the NSA had been listening in on the telephones of several world leaders including Germany's Angela Merkel, who told Obama in October that such action would be a "breach of trust" between two allies.

The hearing came amid growing congressional and public concern over the scope of domestic intelligence gathering.

If the collection programme was debated … [it would have been rejected]

JAMES SENSENBRENNER, CONGRESSMAN

Members of the panel warned the Obama administration to reform the NSA's bulk data collection programme or risk losing authority to conduct such surveillance.

Congressman James Sensenbrenner, an author of the counter-terrorism Patriot Act that followed the attacks of September 11, 2001, said it was a "shock" to learn how it was being used to justify a vast operation to hoover up telephone metadata.

"If the bulk collection programme was debated by the Congress ... it never would have been approved," Sensenbrenner said.

The section of the law used to justify the programme "sunsets" in June 2015, and with bipartisan congressional opposition to bulk data collection mounting, Sensenbrenner and others suggested it would not be reauthorised without an overhaul.

"Unless Section 215 is fixed, Mr Cole, you in the intelligence community will end up getting nothing, because there are not enough votes in Congress" to pass it.

John Conyers, the panel's top Democrat, appeared to side with Sensenbrenner, saying "consensus is growing that this metadata programme is ineffective".

He warned that allowing all of Section 215 to expire would "lose valuable counter-terrorism tools along with the surveillance programmes many of us find objectionable".

Obama said last month that the administration was considering reforming the programme by shifting metadata storage from the government to the telephone companies or a third party.

A key question is whether such reforms are too late. Last year, the House of Representatives came just 12 votes shy of defunding the NSA surveillance programme, and there is pending legislation in the House and Senate that would scrap the programme altogether.

House Judiciary Committee chairman Bob Goodlatte said that transferring storage to private companies "could raise more privacy concerns than it solves" and impede efforts by the intelligence community to connect the dots on possible terrorism cases.

He called for rapid action on reform, saying that many members of Congress were "chomping at the bit to move forward" on legislation to curtail the spying programme.

This article appeared in the South China Morning Post print edition as Even Obama may not be immune to NSA spying